In recent years, a type of mobile communications network known as an ad-hoc network has been developed. An ad-hoc network typically includes a number of geographically-distributed, potentially mobile units, sometimes referred to as “nodes,” which are wirelessly connected to each other by one or more links (e.g., radio frequency communication channels). In this type of network, each mobile node is capable of operating as a base station or router for the other mobile nodes, thus eliminating the need for a fixed infrastructure of base stations.
A wireless mesh network is a collection of wireless nodes or devices organized in a decentralized manner to provide range extension by allowing nodes to be reached across multiple hops. In a multi-hop network, communication packets sent by a source node can be relayed through one or more intermediary nodes before reaching a destination node. A large network can be realized using intelligent access points (IAP) which provide wireless nodes with access to a wired backhaul. A mesh network therefore typically comprises one or more IAPs (Intelligent Access Points), and a number of APs (Access Points), which provide data service to STAs (subscriber stations). An AP can connect to IAP directly or through multi-hop route. More sophisticated ad-hoc networks are also being developed which, in addition to enabling mobile nodes to communicate with each other as in a conventional ad-hoc network, further enable the mobile nodes to access a fixed network and thus communicate with other mobile nodes, such as those on the public switched telephone network (PSTN), and on other networks such as the Internet.
Typically, in a mesh network an IAP communicates with the APs by transmitting and receiving packets on radio channels. In certain cases, the IAP switches the channel on which it is communicating with the APs. For example, the IAP switches its channel when it detects a Radar signal on the channel. If during operation, an IAP detects a radar event over the Radio Frequency (RF) channel that the network backhaul uses, it must immediately change to another available RF channel. This is dictated by Federal Communications Commission (FCC) and European Telecommunications Standards Institute (ETSI) standards, and is established to allow the sharing of the five GigaHertz (5 GHz) spectrum between wireless LAN (WLAN) and military or weather radars that use the same frequencies. Alternatively, the IAP can switch channel if it detects a need for a periodic scan, or if it detects a weak radio link with the APs.
In some traditional mesh systems, it takes significant amount of time for an AP to detect the loss of an IAP when the IAP switches its channel of operation. Conventionally, a mesh AP will detect a lost connection with IAP after missing infrastructure hello frames or by timing out. Also, additional time is spent by the AP in scanning for new channels and then associating with the same or a new IAP. Generally, during the transition period of the channel switch operation at the IAP, associated APs are unable to provide meshing services to their clients.
Accordingly, there is a need for a method and apparatus to select a channel in a wireless communication system to facilitate a smooth channel switch operation.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.